Decrease in Myocardial Ischemic Tolerance with Aging in Fischer 344 Rats
Some animal studies indicate that ischemic tolerance is decreased in the senescent myocardium. However, the results of cardiac operations in the elderly are compatible with those performed in middle-aged people. It is important to determine whether ischemic tolerance may be decreased in middle age. Hearts from young adult (12 weeks old) or the middle-aged (50 weeks old) Fischer 344 rats were subjected to 15, 20, or 25 minutes of global ischemia followed by reperfusion. The recovery of left ventricular function and high-energy phosphates was significantly lower in the hearts of middle-aged rats than in those of the young adult rats after any period of global ischemia. The increase in left ventricular end-diastolic pressure was also greater in the middle-aged rats, although there were no diferences in these indexes in the two age groups before the induction of ischemia. The incidence of reperfusion-induced ventricular fibrillation was significantly higher and the release of creatine kinase in the coronary effluent during reperfusion significantly greater in the middle-aged rats than in the young adult rats. Results indicate that rat hearts are more vulnerable to ischemia, even in middle age.
KeywordsCreatine Kinase Ventricular Tachycardia Creatine Phosphate Global Ischemia Ischemic Tolerance
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